How can I fix my battery for my Galaxy Note ll?

I have a Galaxy Note ll I was having battery issues where once it reached about 30% it would die in twenty minutes. I mentioned this to someone and he rooted my phone for me and did some things to "fix it", but now my phone is completely messed up. After he fixed it he told me to charge it to 100%, use this battery calibration app, let it completely run out of battery, then charge it to 100% after it died while it was still off. I did this, restarted my phone and used it like normal, then a few hours later my phone started freezing up, the battery jumped from 50% all the way to 17% percent and kept locking up. I have no idea what to do.

Once it started freezing up, I tried taking my battery out several times. I didn't charge it while it was off though, other than the first time, does that make any difference?
Also, when I turn it back on after it dies on me it says I have a higher battery amount. The last time I did it, it had been stuck at 3% for twenty minutes, it locked up, after waiting ten minutes I took the battery out for a bit, and turned it back on, it then said that I had 14% battery.

Sounds like the battery to me as well. My Note 2 original battery has been draining really fast the last couple weeks as well and getting worse every day! I started this morning taking my phone off charger and in 1 hour am down to 43%! I am waiting on my ordered Note 4 to arrive!

Wondering if your friend rooting your phone may have messed it up in addition to bad battery.